The present invention relates to a plastic zipper which has a slider and in which hermetic sealing performance is not impaired even by repeated opening and closing operations, a bag body equipped with the plastic zipper and a process for producing the bag body.
Bag bodies each equipped with a plastic zipper are widely employed as packaging materials for a variety of articles in the fields of foods, pharmaceuticals, electronic part items and the like. There have hitherto been proposed various items relating to the structure of this kind of plastic zipper and a slider for opening and closing the same [for instance, Japanese Patent Application Laid-Open No. 214920/1996 (Heisei 8)]. In general, the structure of a plastic zipper is constituted as illustrated in FIG. 20 in which F is a plastic film, F1-1 and F1-2 are each a female hook formed on the plastic film, M1-1 is a male hook, and the zipper is closed when the male hook is inserted in and engaged with the two female hooks.
The slider which is usually employed is composed generally of an outside guide and an inside guide in such a structure that the inside guide is inserted between the male hook and the female hooks and causes the male/female hooks to disengage, while the outside guide sandwiches the male/female hooks therein and causes the male/female hooks to engage. Since in the slider of the conventional structure, the inside guide is inserted between the hooks of a zipper, even if the zipper is completely bound tight, the content in a bag leaks between the hooks and the inside guide which is inserted between the hooks. Hence, the above-mentioned zipper is unusable for applications requiring hermetic sealing except for applications only not requiring hermetic sealing such as general cargoes.
On the other hand, there is proposed a zipper having such a structure that hermetic sealing can be maintained in a state of a bag being closed with a slider by the use of a specially shaped plastic zipper and a slider adapted thereto (for instance, U.S. Pat. Nos. 6,067,208 and 6,664,299). In the plastic zippers as disclosed therein, hermetic sealing performance is maintained by taking advantage of the elasticity of the plastic material which constitutes the zipper for the purpose of facilitating the disengagement even with a weak force, and therefore when the elasticity thereof varies with a variation in temperature or the like, there is caused a fear of incapability of maintaining the hermetic sealing performance after opening and closing operations, whereby the amount of leakage is increased. Such being the case, the above-proposed zippers are unusable for packaging such content as liquid and the like in which occurrence of leakage is forbidden.
The present inventors previously proposed a zipper having good hermetic sealing performance equipped with a sealing portion bondable to the inside of male and female hooks respectively, more specifically, a plastic zipper having good hermetic sealing performance characterized as illustrated in FIG. 21 by forming male hooks M2-1, M2-2 and female hooks F2-1, F2-2 of the zipper on the surface of a plastic film F, forming a continuous tightening wall R1 parallel to the male hooks M2-1, M2-2 on the inside thereof, and further forming a continuous pressing rib R2 parallel to the female hooks F2-1, F2-2 on the inside thereof, so that the zipper is imparted with excellent properties in persistent hermetic sealing performance and also impact resistance by the tight contact between the continuous tightening wall R1 and the continuous pressing rib R2 as well as self-tightening effect thereof (Japanese Patent Registration No. 2,938,784). The plastic zipper is excellent in hermetic sealing performance and impact resistance and almost free from performance variation due to temperature variation, and accordingly is well suited for packaging liquid and the like. However, it remains unsolved to develop a slider that does not impair the hermetic sealing performance of the aforesaid plastic zipper.
Accordingly, the object of the present invention is to solve the disadvantages of the previous plastic zipper fitted with a slider and the previous bag body equipped with the previous plastic zipper, and also to provide a plastic zipper which is fitted with a slider and which is excellent in hermetic sealing performance having a slider that never impairs the hermetic sealing characteristics; a bag body equipped with said zipper; and a process for producing said bag body.
As a result of intensive research and investigation made by the present inventors, it has been made possible to eliminate the previous disadvantage of insufficiency in the hermetic sealing performance and according to a proposal of the present inventors, to develop a plastic zipper which has a slider and is capable of assuring sealing characteristics, a bag body equipped with said zipper and also a process for producing said bag body. The present invention has been accomplished on the basis of this development.
That is, the present invention provides a plastic zipper with a slider, comprising a pair of male hook and female hook formed on plastic films and a slider by which the zipper is opened and closed, wherein the zipper is equipped with protrusions serving as a guide for the slider which are installed parallel to the male and female hooks, respectively on the side of an opening portion of the zipper, and the slider is equipped with an inside guide which engages with the protrusions so that the inside guide is positioned between the protrusions and the hooks on the side of the opening portion of the zipper.
At the same time, the present invention provides said plastic zipper wherein the inside guide is formed in a bilaterally asymmetrical manner, and is constituted such that in a step of opening operation, it opens the female hook outward, thereafter opens the male hook, and subsequently opens the protrusions to a large extent at the opening end of the slider, thus opening the zipper portion.
Also, said plastic zipper has hollows which allow the inside guide of the slider to fit therein are installed on the opening side of the zipper end portion.
Further, the plastic zipper is a hermetic sealing zipper that is equipped with a bondable sealing portion inside the male hook and a bondable sealing portion inside the female hook separately from a locking portion of the zipper.
Furthermore, the bag body according to the present invention is equipped with the plastic zipper which has the slider and which is characterized by the preceding description.
The length of heat seal to be overhanged to the inside of the bag at the closing end of the plastic zipper with the slider is set on a length equal to or more than the distance between the closing end of the slider and the opening end thereof.
The process for producing the bag body of the present invention is characterized by a guide-constituting member equipped with an inside guide portion has opening ability and closing ability formed through a flexural portion having an axis for flexure perpendicularly intersecting a plane containing a bag body, is attached to a slider body so as to constitute a slider, the slider is mounted on a zipper in a state that the guide-constituting member is opened through the flexural portion, and subsequently the guide-constituting member is closed through the flexural portion, thereby accomplishing the mounting of the slider onto the zipper.